Oxide etch selectivity systems and methods

ABSTRACT

Embodiments of the present technology may include a method of etching a substrate. The method may include striking a plasma discharge in a plasma region. The method may also include flowing a fluorine-containing precursor into the plasma region to form a plasma effluent. The plasma effluent may flow into a mixing region. The method may further include introducing a hydrogen-and-oxygen-containing compound into the mixing region without first passing the hydrogen-and-oxygen-containing compound into the plasma region. Additionally, the method may include reacting the hydrogen-and-oxygen-containing compound with the plasma effluent in the mixing region to form reaction products. The reaction products may flow through a plurality of openings in a partition to a substrate processing region. The method may also include etching the substrate with the reaction products in the substrate processing region.

TECHNICAL FIELD

The present technology relates to semiconductor systems, processes, andequipment. More specifically, the present technology relates to systemsand methods for etching semiconductor materials.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Dry etches produced in local plasmas formed within the substrateprocessing region can penetrate more constrained trenches and exhibitless deformation of delicate remaining structures than wet etches.However, even though an etch process may be selective to a firstmaterial over a second material, some undesired etching of the secondmaterial may still occur.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

BRIEF SUMMARY

Embodiments of the present technology includes methods and systems forselective etching. High etch selectivities of silicon oxide overmaterials including polysilicon and silicon nitride are achieved. Anadditional partition defining a plurality of openings may affect theflow of compounds and enhance or suppress certain reactions. In somecases, the additional partition may increase the residence time and/orthe mixing of plasma products with a hydrogen-and-oxygen-containingcompound. The plasma products and the hydrogen-and-oxygen-containingcompound may react to reduce the concentration of compounds that mayetch materials that are not targeted for etch. Additionally, thepartition may aid the formation of other compounds that may etch siliconoxide or other materials targeted for etch. The partition may thenincrease the etch selectivity compared to a process or system withoutthe partition.

Embodiments of the present technology may include a method of etching asubstrate. The method may include striking a plasma discharge in aplasma region. The method may also include flowing a fluorine-containingprecursor into the plasma region to form a plasma effluent. The plasmaeffluent may flow into a mixing region. The method may further includeintroducing a hydrogen-and-oxygen-containing compound into the mixingregion without first passing the hydrogen-and-oxygen-containing compoundinto the plasma region. Additionally, the method may include reactingthe hydrogen-and-oxygen-containing compound with the plasma effluent inthe mixing region to form reaction products. The reaction products mayflow through a plurality of openings in a partition to a substrateprocessing region. The method may also include etching the substratewith the reaction products in the substrate processing region.

Embodiments may include a substrate processing system. The system mayinclude a first gas inlet, a pedestal configured to support a substrate,a showerhead, a partition, a second gas inlet, and a power supply. Theshowerhead may be an electrically conductive plate defining a pluralityof openings. The showerhead may also be positioned between the first gasinlet and the pedestal. The partition may define a second plurality ofopenings and may be positioned between the pedestal and the showerhead.The second gas inlet may be positioned at the showerhead or between theshowerhead and the partition. A plasma region may be defined between thefirst gas inlet and the showerhead. A substantially plasma-free regionmay be defined between the showerhead and the partition. A substrateprocessing region may be defined between the partition and the pedestal.The power supply may be configured to strike a plasma discharge in theplasma region.

Embodiments may also include a method of etching a substrate. The methodmay include striking a first plasma discharge in a first plasma region.The method may also include striking a second plasma discharge in asecond plasma region. The method may further include flowing afluorine-containing precursor into the first plasma region to form aplasma effluent. The plasma effluent may flow into the second plasmaregion. In the second plasma region, a hydrogen-and-oxygen-containingcompound and the plasma effluent may react to form reaction products.The hydrogen-and-oxygen-containing compound may not be excited by thefirst plasma prior to entering the second plasma region. The method mayadditionally include flowing the reaction products through a pluralityof openings in a partition to a substrate processing region. The methodmay also include etching the substrate with the reaction products in thesubstrate processing region.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodimentsmay be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a block flow diagram of a method of etching according toembodiments.

FIG. 2 shows a simplified diagram of a substrate processing systemaccording to embodiments.

FIG. 3 shows a block flow diagram of a method of etching according toembodiments.

FIG. 4 shows a simplified diagram of a substrate processing systemaccording to embodiments.

FIG. 5 shows etch selectivities for different processes according toembodiments.

FIG. 6 shows a schematic cross-sectional view of a substrate processingchamber according to embodiments.

FIG. 7 shows a schematic cross-sectional view of a portion of asubstrate processing chamber according to embodiments.

FIG. 8 shows a bottom view of a showerhead according to embodiments.

FIG. 9 shows a top view of an exemplary substrate processing systemaccording to embodiments.

DETAILED DESCRIPTION

Conventional methods and systems of etching materials may have lowerthan desired etch selectivities as characteristic dimensions ofsemiconductor structures decreases. In some processes, a lower qualityoxide must be etched more quickly than a higher quality oxide. The oxideetch rate may be lowered in order to increase selectivity between oxidetypes. In this lower oxide etch regime, etch selectivity between oxideand silicon or silicon nitride may decrease. The undesired etch ofsilicon or silicon nitride may have detrimental impacts on deviceperformance, particularly with smaller and smaller semiconductordevices.

Embodiments of the present technology increase, over conventionalmethods and systems, the etch selectivity of oxide to silicon, siliconnitride, or other materials. An additional partition in the processalters the flow and reactions of precursors and compounds in the etchprocess. The partition may be positioned downstream of a plasma regionand downstream of the introduction of a hydrogen-and-oxygen-containingcompound. The partition may reduce the concentration of species that mayetch silicon and silicon nitride (e.g., fluorine radicals), whileincreasing the formation of species that etch silicon oxide (e.g., HF₂⁻). Hence, etch selectivities of oxide to polysilicon, silicon nitride,and/or other materials may increase over methods and systems without thepartition.

FIG. 1 shows a method 100 of etching a substrate according toembodiments. The method may include striking a plasma discharge in aplasma region (block 102). The plasma discharge may be a capacitivelycoupled plasma or an inductively coupled plasma. Method 100 may alsoinclude flowing a fluorine-containing precursor into the plasma regionto form a plasma effluent (block 104). The fluorine-containing precursormay include a precursor selected from the group consisting of atomicfluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride,hydrogen fluoride, and xenon difluoride. Other gases may be flowed intothe plasma region along with the fluorine-containing precursor. Othergases may include, for example, an inert gas, a noble gas, helium,and/or argon. Other sources of oxygen may be used to augment or replacethe nitrogen trifluoride. In general, an oxygen-containing precursor isflowed into the plasma region and the fluorine-containing precursorcomprises at least one precursor selected from the group consisting ofmolecular oxygen (O₂), ozone (O₃), dinitrogen oxide (N₂O), hyponitrite(N₂O₂) or nitrogen dioxide (NO₂) in embodiments. The plasma effluent mayinclude atoms, molecules, radicals, and/or ions of the molecules in thegas present before being excited by the plasma discharge.

In addition, method 100 may include flowing the plasma effluent into amixing region (block 106). The plasma effluent may flow through aplurality of openings in a showerhead. The mixing region may besubstantially plasma-free. “Plasma-free” does not necessarily mean theregion is devoid of plasma. Ionized species and free electrons createdwithin the plasma region may travel through the openings in theshowerhead at exceedingly small concentrations. The borders of theplasma in the chamber plasma region may encroach to some small degreeupon the regions downstream of the showerhead through the openings inthe showerhead. Furthermore, a low intensity plasma may be created in aregion downstream of the showerhead without eliminating desirablefeatures of the etch processes described herein. All causes for a plasmahaving much lower intensity ion density than the chamber plasma regionduring the creation of the excited plasma effluents do not deviate fromthe scope of “plasma-free” as used herein.

In some embodiments, method 100 may further include introducing ahydrogen-and-oxygen-containing compound into the mixing region (block108) without first passing the hydrogen-and-oxygen-containing compoundinto the plasma region. The hydrogen-and-oxygen-containing compound maynot be excited or ionized by any plasma outside the mixing region priorto entering the mixing region. If the hydrogen-and-oxygen-containingcompound were introduced in the same gas inlet as thefluorine-containing precursor, the hydrogen-and-oxygen-containingcompound may disassociate, ionize, or undergo other reactions orexcitations, which may affect etch reactions and increase processcomplexity. Instead, the hydrogen-and-oxygen-containing compound may beintroduced downstream of the plasma in order to deliver the compoundwithout dissociating and without unnecessarily increasing processcomplexity. The hydrogen-and-oxygen-containing compound may includewater vapor or an alcohol. The alcohol may include one or more ofmethanol, ethanol, and isopropyl alcohol in embodiments. Thehydrogen-and-oxygen-containing compound may include an O—H bond.

Additionally, method 100 may include reacting thehydrogen-and-oxygen-containing compound with the plasma effluent in themixing region to form reaction products (block 110). A reaction in themixing region may include fluorine radical and water reactants. Thefluorine radical and water may react to form products, including HF₂ ⁻and OH⁻. The reaction products may include combinations of hydrogen,fluorine, and/or oxygen atoms.

The method may further include flowing reaction products through aplurality of openings in a partition to a substrate processing region(block 112). The substrate processing region may be substantially orentirely plasma-free. Each opening of a portion of the plurality ofopenings in the partition may or may not be concentrically aligned withthe nearest opening of the plurality of openings in the showerhead. Theportion of the plurality of openings that may or may not beconcentrically aligned may or may not be the entirety of the openings inthe partition. Without intending to be bound to any particular theory,it is believed that the partition enhances mixing between the plasmaeffluent and the hydrogen-and-oxygen-containing compound. Specifically,the partition may increase reactions between F radicals and water andtherefore may reduce F radicals that may etch polysilicon, siliconnitride, or other materials.

Method 100 may also include etching the substrate with the reactionproducts in the substrate processing region (block 114). The substratemay include a semiconductor wafer with patterned layers on top of thewafer. The substrate may include an exposed silicon oxide portion and asecond exposed portion. The second exposed portion may have acompositional atomic ratio other than 1 silicon atom to 2 oxygen atoms.The silicon oxide may etch by a mechanism including the followingreactions:—Si—O⁻+H⁺→—Si—OH  (1)—Si—OH+HF₂ ⁻→—Si—F+OH⁻+HF  (2).Reaction (1) shows how the surface of silicon oxide may be protonated bya hydrogen ion, which may have been formed in the mixing region.Reaction (2) shows how the protonated surface may be attacked by HF₂ ⁻to form fluorinated silicon. After silicon reacts with three morefluorine atoms, SiF₄ is formed and desorbs from the surface. Theadditional three fluorine atoms may come from fluorine radicals and/orHF₂ ⁻.

In embodiments, the second exposed portion may include polysilicon orsilicon nitride. The first exposed portion may etch at an etch rate over500 times faster than the polysilicon etches. In some cases, the etchrate may be over 600 times, 700 times, 800 times, 900 times, 1,000 timesfaster. In addition, the first exposed portion may etch at an etch rateat over 200 times faster than the silicon nitride etches. For example,the etch rate for silicon oxide over silicon nitride may be over 250times faster, 300 times faster, 350 times faster, or 400 times faster.In some embodiments, the substrate may include two types of siliconoxide. One type of silicon oxide may etch faster, but less than 2 timesfaster, than the other type of silicon oxide. Process temperatures maybe from 0° C. to 100° C., including from 8° C. to 15° C. Processpressures may be from 0.5 torr to 12 torr.

Embodiments may include a substrate processing system 200, shown in FIG.2. The system may include a first gas inlet 202, a pedestal 204configured to support a substrate 206, a showerhead 208, a partition210, a second gas inlet 212, and a power supply 214. First gas inlet 202may be configured to receive gas from first gas source 203. Partition210 may be disposed from 1,000 to 4,000 mils away from showerhead 208,including, for example, from 1,000 to 1,500 mils, from 1,500 to 2,000mils, from 2,000 to 2,500 mils, from 2,500 to 3,000 mils, from 3,000 to3,500 mils, or from 3,500 to 4,000 mils. Pedestal 204 may be disposed1,000 to 4,000 mils from the surface of showerhead 208 facing thepartition 210. For instance, pedestal 204 may be between 1,000 and 1,500mils, 1,500 and 2,000 mils, 2,000 and 2,500 mils, 2,500 and 3,000 mils,3,000 and 3,500 mils, or 3,500 and 4,000 mils from the surface ofshowerhead 208 opposite the partition. Partition 210 may be circular.Partition 210 may be called a flow distribution plate or a distributionplate. Partition 210 may be positioned at any distance betweenshowerhead 208 and pedestal 204. In embodiments, partition 210 is about2,800 mil from showerhead 208, and pedestal 204 may be positioned from2,800 to 4,000 mil from showerhead 208.

Showerhead 208 may be an electrically conductive plate defining aplurality of openings, including opening 216. Each opening of theplurality of openings in showerhead 208 may be cylindrical. In someembodiments, opening 216 may include a cylindrical portion and a taperedportion or portions. The tapered portion may taper away from or towardthe pedestal. Opening 216 may include a cylindrical portion bounded bytwo tapered portions. Showerhead 208 may also be positioned betweenfirst gas inlet 212 and pedestal 204. Partition 210 may define a secondplurality of openings and may be positioned between pedestal 204 andshowerhead 208. Each opening of the plurality of openings in partition210 may be cylindrical. Opening 218 is an example of one opening inpartition 210. The diameter of each opening in the plurality of openingsin showerhead 208 may be equal to the diameter of each opening in theplurality of openings in partition 210. In embodiments, the plurality ofopenings in at least one of showerhead 208 and partition 210 may have anon-uniform distribution of hole sizes. Showerhead 208 may be circularand may have the same diameter as partition 210. Showerhead 208 may havea diameter within 10%, 20%, 30%, 40%, or 50% of the diameter ofpartition 210.

Second gas inlet 212 may be positioned at showerhead 208 or betweenshowerhead 208 and partition 210. Second gas inlet 212 may deliver gasfrom a second gas source 220 to apertures 222 in showerhead 208.Apertures 222 may direct gas toward partition 210 and not direct gas tomix with plasma effluent in opening 216. In this manner, showerhead 208may be a dual channel showerhead. No gas inlet may be positioned at thesame level as partition 210. A plasma region 224 may be defined betweenfirst gas inlet 202 and showerhead 208.

A substantially plasma-free region 226 may be defined between showerhead208 and partition 210. A substrate processing region 228 may be definedbetween partition 210 and pedestal 204. A plurality of gas outlets,including gas outlet 230, may be positioned between partition 210 andpedestal 204. The plurality of gas outlets may lead to a pump 232. Theplurality of gas outlets may be arranged at a radius about a centerpoint. The center point may be located on a line through the center ofshowerhead 208 and the center of partition 210. The plurality of gasoutlets may be distributed uniformly along the circumference of a circlehaving the radius about the center point. No gas inlet may deliver gasdirectly into the substrate processing region.

In some embodiments, no gas outlets may be positioned between partition210 and pedestal 204. The lack of gas outlets in substrate processingregion 228 may be a result of the system not have gas outlets at thislocation or a pump liner fit over gas outlets to prevent gas flowthrough the outlets. The only gas outlet may be on the side of pedestal204 opposite partition 210. Forcing gas to exit under the pedestalrather than radially out the plurality of gas outlets may improve etchuniformity.

Power supply 214 may be configured to strike a plasma discharge inplasma region 224. Power supply 214 may be an RF power supply. Powersupply 214 for a capacitively coupled plasma may operate from 0 W to2000 W, including, for example, 25 W to 500 W.

In some embodiments, an ion suppressor may be positioned between theshowerhead and the first gas inlet. The ion suppressor may include athird plurality of openings. The ion suppressor may be circular and mayhave the same diameter as the showerhead. The ion suppressor may have adiameter within 10%, 20%, 30%, 40%, or 50% of the diameter of theshowerhead. The third plurality of openings may have a non-uniformdistribution of opening diameters. Possible examples of an ionsuppressor are described in more detail below. Any two or three of theion suppressor, the showerhead, and the partition may have an identicalpattern or distribution of plurality of openings. In embodiments, anytwo of or three of the ion suppressor, the showerhead, and the partitionmay have a different pattern or distribution of plurality of openings.

As shown in FIG. 3, embodiments may also include a method 300 of etchinga substrate. Method 300 may include striking a first plasma discharge ina first plasma region (block 302). The first plasma discharge may be aremote plasma. The remote plasma source may have a power between 0 kWand 10 kW.

Method 300 may also include striking a second plasma discharge in asecond plasma region (block 304). The second plasma discharge may be inthe same chamber as the substrate. The second plasma may be acapacitively coupled plasma or an inductively coupled plasma. The powersource for the second plasma discharge may operate from 0 W to 500 W.Method 300 may further include flowing a fluorine-containing precursorinto the first plasma region to form a plasma effluent (block 306).Method 300 may include flowing the plasma effluent into the secondplasma region (block 308). In the second plasma region, ahydrogen-and-oxygen-containing compound and the plasma effluent mayreact to form reaction products (block 310). Thehydrogen-and-oxygen-containing compound may not be excited by the firstplasma prior to entering the second plasma region. Method 300 mayadditionally include flowing the reaction products through a pluralityof openings in a partition to a substrate processing region (block 312).Method 300 may also include etching the substrate with the reactionproducts in the substrate processing region (block 314).

The plasma effluent may not flow through a plurality of openings in anelectrically grounded showerhead and/or ion suppressor before the plasmaeffluent enters the second plasma region and after entering an etchchamber. The second plasma discharge may not be formed by an electricalconnection to a showerhead or ion suppressor. The second plasma regionmay not include or be bounded by a showerhead or an ion suppressordescribed herein. Without intending to be bound by any particulartheory, it is believed that the remote plasma unit in combination with asecond plasma discharge provides adequate mixing and reaction of theplasma effluent and the hydrogen-and-oxygen-containing compound toincrease etch selectivity of the oxide over other materials.

A system used to implement method 300 may include system 400 in FIG. 4.Overall, system 400 in FIG. 4 is similar to system 200 in FIG. 2 withthe addition of a Remote Plasma Source (RPS) Unit 402 and the omissionof a showerhead. In system 400, first gas source 404 delivers gas to RPSUnit 402. RPS Unit 402 is configured to strike a plasma discharge andmay generate plasma effluents. Plasma effluents may flow down gas inlet406. Gas inlet 406 may be substantially plasma-free.

Plasma effluents may flow into a second plasma region 408. Second plasmaregion 408 may be between gas inlet 406 and a partition 410. The secondplasma region may include a plasma discharge, which may be sustainedwith power from power supply 412. Power supply 412 may be an RF powersupply capacitively coupled between the chamber and partition 410. Asecond gas inlet 414 may deliver gas from a second gas source 416.Second gas source 416 may include water or anotherhydrogen-and-oxygen-containing compound. The reaction products formed inthe second plasma region may flow through a plurality of openings inpartition 410, such as opening 418. The reaction products may then be ina substrate processing region 420, defined as between partition 410 andpedestal 422. Substrate processing region 420 may be substantiallyplasma-free. Even so, the gas in substrate processing region 420 mayetch a portion of substrate 424.

As with system 200, system 400 may include a gas outlet 426 leading topump 428. Gas outlet 426 may be in a similar position and configurationas gas outlet 230 in FIG. 2. Additionally, system 400 may exclude gasoutlet 426 and other similar gas outlets in substrate processing region420.

Generally speaking, the methods presented herein may be used toselectively etch silicon oxide relative to a wide variety of materialsand not just polysilicon and silicon nitride. The methods may be used toselectively etch exposed silicon oxide faster than titanium, titaniumnitride, titanium oxide, titanium silicide, hafnium, hafnium oxide,hafnium silicide, tantalum, tantalum oxide, tantalum nitride, tantalumsilicide, cobalt, cobalt oxide, cobalt silicide, tungsten, tungstenoxide, tungsten silicide, silicon carbide, silicon nitride, siliconoxynitride, silicon carbon nitride, C—H films, C—H—N films, silicongermanium, germanium, nickel, nickel oxide, or nickel silicide.

The second exposed portion may include at least one element from thegroup consisting of nitrogen, hafnium, titanium, cobalt, carbon,tantalum, tungsten, and germanium according to embodiments. The secondexposed portion may consist essentially of or consist of a compositionselected from the group of silicon, tantalum, tantalum and oxygen,tantalum and silicon, tantalum and nitrogen, cobalt, cobalt and oxygen,cobalt and silicon, tungsten, tungsten and oxygen, tungsten and silicon,nickel, nickel and oxygen, nickel and silicon, silicon and nitrogen,silicon and oxygen and nitrogen, silicon and carbon and nitrogen,silicon and carbon, carbon, carbon and hydrogen, carbon and hydrogen andnitrogen, silicon and germanium, germanium, hafnium, hafnium and oxygen,hafnium and silicon, titanium, titanium and oxygen, titanium andnitrogen, or titanium and silicon in embodiments.

EXAMPLE

Etch methods with a distribution plate were tested for etch selectivityagainst other processes without a distribution plate. Results for thevarious methods are shown in FIG. 5. The results for the first column isthe control recipe for etching oxide. The bars indicate that the etchselectivity of oxide to polysilicon is greater than 200 and the etchselectivity of oxide to low pressure silicon nitride (“LP SiN”) is about100. The second column of FIG. 5 shows results for an etch processtermed uSMD, which includes a different ion suppressor, where the ionsuppressor has a different distribution of openings and/or diameters ofthe openings. SMD stands for selectivity modulation device, which is anion suppressor. The third column shows the showerhead with the uSMDdistribution of openings and a recipe including helium. The results showa slight increase in etch selectivity of oxide to polysilicon and aboutthe same etch selectivity of oxide to low pressure silicon nitride.However, as a result of the slow etch rate of polysilicon and/orexperimental precision, the difference in the selectivity between thethird column and the first two columns does not translate to adifference when used in typical manufacturing processes. The first threecolumns show that a different ion suppressor configuration and adifferent recipe have little effect on etch selectivities.

The fourth column shows etch selectivity results for a chamber with anadditional flow distribution plate with the recipe of the third column.The etch selectivity of oxide to polysilicon has increased to about andabove 800, and the etch selectivity of oxide to low pressure siliconnitride has increased to close to 300. The fifth column includes theconditions of the fourth column and a pump liner skirt to cover gasoutlets on the chamber wall between the pedestal and the flowdistribution plate. The etch selectivity under the conditions of thefifth column are similar to that of the fourth column, indicating thatpump liner skirt does not affect etch selectivity.

Also shown on FIG. 5 are the etch selectivities of the oxide to a higherquality oxide. Neither the oxide nor the higher quality oxide is athermal oxide. The higher quality oxide may have a higher density anddifferent surface conditions than the oxide. A higher anneal temperaturefor the higher quality oxide may make the higher quality oxide moredifficult to etch. The etch selectivity between the two oxides is aboutthe same regardless of chamber configuration and recipe. FIG. 5 alsoshows the etch selectivity between oxide and plasma enhanced siliconnitride (“PE SiN”), which is also about the same across differentprocess conditions. Plasma enhanced silicon nitride may have a higherhydrogen content than low pressure silicon nitride, and as a result theetch mechanism may be similar to oxide instead of polysilicon or lowpressure silicon nitride. Hence, the selectivity of the etch to plasmaenhanced silicon nitride may not increase much. These results show thatthe addition of the flow distribution plate does not have a negativeimpact on other etch selectivities.

Exemplary Processing Systems

FIG. 6 shows a cross-sectional view of an exemplary substrate processingchamber 1001 with a partitioned plasma generation region within theprocessing chamber. During film etching, a process gas may be flowedinto chamber plasma region 1015 through a gas inlet assembly 1005. Aremote plasma system (RPS) 1002 may optionally be included in thesystem, and may process a first gas which then travels through gas inletassembly 1005. The process gas may be excited within RPS 1002 prior toentering chamber plasma region 1015. Accordingly, thefluorine-containing precursor as discussed above, for example, may passthrough RPS 1002 or bypass the RPS unit in embodiments.

A cooling plate 1003, faceplate 1017, ion suppressor 1023, showerhead1025, and a substrate support 1065 (also known as a pedestal), having asubstrate 1055 disposed thereon, are shown and may each be includedaccording to embodiments. Pedestal 1065 may have a heat exchange channelthrough which a heat exchange fluid flows to control the temperature ofthe substrate. This configuration may allow the substrate 1055temperature to be cooled or heated to maintain relatively lowtemperatures, such as between −20° C. to 200° C. Pedestal 1065 may alsobe resistively heated to relatively high temperatures, such as between100° C. and 1100° C., using an embedded heater element.

Exemplary configurations may include having the gas inlet assembly 1005open into a gas supply region 1058 partitioned from the chamber plasmaregion 1015 by faceplate 1017 so that the gases/species flow through theholes in the faceplate 1017 into the chamber plasma region 1015.Structural and operational features may be selected to preventsignificant backflow of plasma from the chamber plasma region 1015 backinto the supply region 1058, gas inlet assembly 1005, and fluid supplysystem 1010. The structural features may include the selection ofdimensions and cross-sectional geometries of the apertures in faceplate1017 to deactivate back-streaming plasma. The operational features mayinclude maintaining a pressure difference between the gas supply region1058 and chamber plasma region 1015 that maintains a unidirectional flowof plasma through the showerhead 1025. The faceplate 1017, or aconductive top portion of the chamber, and showerhead 1025 are shownwith an insulating ring 1020 located between the features, which allowsan AC potential to be applied to the faceplate 1017 relative toshowerhead 1025 and/or ion suppressor 1023. The insulating ring 1020 maybe positioned between the faceplate 1017 and the showerhead 1025 and/orion suppressor 1023 enabling a capacitively coupled plasma (CCP) to beformed in the chamber plasma region.

The plurality of holes in the ion suppressor 1023 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 1023. For example,the aspect ratio of the holes, or the hole diameter to length, and/orthe geometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 1023 is reduced. The holes in the ion suppressor 1023 mayinclude a tapered portion that faces chamber plasma region 1015, and acylindrical portion that faces the showerhead 1025. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 1025. An adjustable electrical biasmay also be applied to the ion suppressor 1023 as an additional means tocontrol the flow of ionic species through the suppressor. The ionsuppression element 1023 may function to reduce or eliminate the amountof ionically charged species traveling from the plasma generation regionto the substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.

Plasma power can be of a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma maybe provided by RF power delivered to faceplate 1017 relative to ionsuppressor 1023 and/or showerhead 1025. The RF power may be betweenabout 10 watts and about 5000 watts, between about 100 watts and about2000 watts, between about 200 watts and about 1500 watts, or betweenabout 200 watts and about 1000 watts in embodiments. The RF frequencyapplied in the exemplary processing system may be low RF frequenciesless than about 200 kHz, high RF frequencies between about 10 MHz andabout 15 MHz, or microwave frequencies greater than or about 1 GHz inembodiments. The plasma power may be capacitively-coupled (CCP) orinductively-coupled (ICP) into the remote plasma region.

Gas may flow from showerhead 1025 to a mixing region 1070. Mixing region1070 may be bounded on one side by a flow distribution plate 1072. Flowdistribution plate may be any partition described herein, and anypartition herein may be flow distribution late 1072. Flow distributionplate 1072 may have a plurality of openings, such as opening 1074.Opening 1074 may include a tapered portion that faces substrateprocessing region 1033, a tapered portion that faces showerhead 1025,and/or a cylindrical portion. The tapered portions may taper toward oraway from the side they face.

A precursor, for example a fluorine-containing precursor and anoxygen-containing precursor, may be flowed into substrate processingregion 1033 by embodiments of the showerhead described herein. Excitedspecies derived from the process gas in chamber plasma region 1015 maytravel through apertures in the ion suppressor 1023, and/or showerhead1025 and react with an additional precursor flowing into substrateprocessing region 1033 from a separate portion of the showerhead.Alternatively, if all precursor species are being excited in chamberplasma region 1015, no additional precursors may be flowed through theseparate portion of the showerhead. Little or no plasma may be presentin substrate processing region 1033 during the remote plasma etchprocess. Excited derivatives of the precursors may combine in the regionabove the substrate and/or on the substrate to etch structures or removespecies from the substrate.

The processing gases may be excited in chamber plasma region 1015 andmay be passed through the showerhead 1025 to substrate processing region1033 in the excited state. While a plasma may be generated in substrateprocessing region 1033, a plasma may alternatively not be generated inthe processing region. In one example, the only excitation of theprocessing gas or precursors may be from exciting the processing gasesin chamber plasma region 1015 to react with one another in substrateprocessing region 1033. As previously discussed, this may be to protectthe structures patterned on substrate 1055.

FIG. 7 shows a detailed view of the features affecting the processinggas distribution through faceplate 1017. The gas distribution assembliessuch as showerhead 1025 for use in the processing chamber section 1001may be referred to as dual channel showerheads (DCSH) and areadditionally detailed in the embodiments described in FIG. 6 as well asFIG. 8 herein. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 1033 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 1025 may comprise an upper plate 1014 and a lower plate1016. The plates may be coupled with one another to define a volume 1018between the plates. The coupling of the plates may be so as to providefirst fluid channels 1019 through the upper and lower plates, and secondfluid channels 1021 through the lower plate 1016. The formed channelsmay be configured to provide fluid access from the volume 1018 throughthe lower plate 1016 via second fluid channels 1021 alone, and the firstfluid channels 1019 may be fluidly isolated from the volume 1018 betweenthe plates and the second fluid channels 1021. The volume 1018 may befluidly accessible through a side of the gas distribution assembly 1025.Although the exemplary system of FIGS. 6-8 includes a dual-channelshowerhead, it is understood that alternative distribution assembliesmay be utilized that maintain first and second precursors fluidlyisolated prior to substrate processing region 1033. For example, aperforated plate and tubes underneath the plate may be utilized,although other configurations may operate with reduced efficiency or notprovide as uniform processing as the dual-channel showerhead described.

In the embodiment shown, showerhead 1025 may distribute via first fluidchannels 1019 process gases which contain plasma effluents uponexcitation by a plasma in chamber plasma region 1015. In embodiments,the process gas introduced into RPS 1002 and/or chamber plasma region1015 may contain fluorine, e.g., NF₃. The process gas may also include acarrier gas such as helium, argon, nitrogen (N₂), etc. Plasma effluentsmay include ionized or neutral derivatives of the process gas and mayalso be referred to herein as a radical-fluorine precursor referring tothe atomic constituent of the process gas introduced. Ahydrogen-and-oxygen-containing compound may flow through second fluidchannels 1021.

FIG. 8 is a bottom view of a showerhead 1025 for use with a processingchamber in embodiments. Showerhead 1025 corresponds with the showerheadshown in FIG. 6. Through-holes 1031, which show a view of first fluidchannels 1019, may have a plurality of shapes and configurations tocontrol and affect the flow of precursors through the showerhead 1025.Small holes 1027, which show a view of second fluid channels 1021, maybe distributed substantially evenly over the surface of the showerhead,even amongst the through-holes 1031, which may help to provide more evenmixing of the precursors as they exit the showerhead than otherconfigurations.

The chamber plasma region 1015 or a region in an RPS may be referred toas a remote plasma region. In embodiments, the radical-fluorineprecursor and the radical-oxygen precursor are created in the remoteplasma region and travel into the substrate processing region to combinewith the hydrogen-and-oxygen-containing precursor. In embodiments, thehydrogen-and-oxygen-containing precursor is excited only by theradical-fluorine precursor and the radical-oxygen precursor. Plasmapower may essentially be applied only to the remote plasma region inembodiments to ensure that the radical-fluorine precursor and theradical-oxygen precursor provide the dominant excitation.

Embodiments of the dry etch systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 9 showsone such processing system (mainframe) 1101 of deposition, etching,baking, and curing chambers in embodiments. In the figure, a pair offront opening unified pods (load lock chambers 1102) supply substratesof a variety of sizes that are received by robotic arms 1104 and placedinto a low pressure holding area 1106 before being placed into one ofthe substrate processing chambers 1108 a-f. A second robotic arm 1110may be used to transport the substrate wafers from the holding area 1106to the substrate processing chambers 1108 a-f and back. Each substrateprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 1020 at rates between about 1 sccm andabout 40 sccm, between about 3 sccm and about 25 sccm or between about 5sccm and about 10 sccm in embodiments. Oxygen (or anotheroxygen-containing precursor) may be flowed into chamber plasma region1020 at rates between about 10 sccm and about 400 sccm, between about 30sccm and about 250 sccm or between about 50 sccm and about 150 sccm inembodiments. Water vapor may be flowed into mixing region 1070 at ratesbetween about 5 sccm and about 100 sccm, between about 10 sccm and about50 sccm or between about 15 sccm and about 25 sccm according toembodiments. The flow rate ratio of the oxygen-containing precursor tothe fluorine-containing precursor may be greater than 4, greater than 6or greater than 10 according to embodiments. The flow rate ratio of theoxygen-containing precursor to the fluorine-containing precursor may beless than 40, less than 30 or less than 20 in embodiments. Upper limitsmay be combined with lower limits according to embodiments.

The showerhead may be referred to as a dual-channel showerhead as aresult of the two distinct pathways into the substrate processingregion. The fluorine-containing precursor and the oxygen-containingprecursor may be flowed through the through-holes in the dual-zoneshowerhead and the water vapor may pass through separate zones in thedual-zone showerhead. The separate zones may open into the mixing regionor the substrate processing region but not into the remote plasma regionas described above.

Combined flow rates of water vapor and plasma effluents into thesubstrate processing region may account for 0.05% to about 20% by volumeof the overall gas mixture; the remainder being carrier gases. Thefluorine-containing precursor and the oxygen-containing precursor flowedinto the remote plasma region but the plasma effluents has the samevolumetric flow ratio, in embodiments. In the case of thefluorine-containing precursor, a purge or carrier gas may be firstinitiated into the remote plasma region before those of thefluorine-containing gas and the oxygen-containing precursor to stabilizethe pressure within the remote plasma region.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon oxide” of thepatterned substrate is predominantly SiO₂ but may include concentrationsof other elemental constituents such as, e.g., nitrogen, hydrogen, andcarbon. In some embodiments, silicon oxide portions etched using themethods disclosed herein consist essentially of silicon and oxygen.Exposed “silicon nitride” of the patterned substrate is predominantlySi₃N₄ but may include concentrations of other elemental constituentssuch as, e.g., oxygen, hydrogen and carbon. In some embodiments, siliconnitride portions described herein consist essentially of silicon andnitrogen. Exposed “hafnium oxide” of the patterned substrate ispredominantly hafnium and oxygen but may include small concentrations ofelements other than hafnium and oxygen. In some embodiments, hafniumoxide portions described herein consist essentially of hafnium andoxygen. Exposed “tungsten” of the patterned substrate is predominantlytungsten but may include small concentrations of elements other thantungsten. In some embodiments, tungsten portions described hereinconsist essentially of tungsten. Analogous definitions apply to allmaterials described herein.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excited state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents (agas in an excited state which is exiting a plasma) which participate ina reaction to either remove material from or deposit material on asurface. “Radical-fluorine precursors” describe radical precursors whichcontain fluorine but may contain other elemental constituents.“Radical-oxygen precursors” describe radical precursors which containoxygen but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Additionally, details of any specific embodiment maynot always be present in variations of that embodiment or may be addedto other embodiments.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neither,or both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a method” includes aplurality of such methods and reference to “the plasma effluent”includes reference to one or more plasma effluents and equivalentsthereof known to those skilled in the art, and so forth. The inventionhas now been described in detail for the purposes of clarity andunderstanding. However, it will be appreciated that certain changes andmodifications may be practice within the scope of the appended claims.

The invention claimed is:
 1. A method of etching a substrate, the methodcomprising: striking a plasma discharge in a plasma region with a powerfrom a power supply; flowing a fluorine-containing precursor into theplasma region to form a plasma effluent; flowing the plasma effluentthrough a first plurality of openings in a showerhead into a mixingregion; introducing a hydrogen-and-oxygen-containing compound into themixing region without first passing the hydrogen-and-oxygen-containingcompound into the plasma region and without flowing thehydrogen-and-oxygen-containing compound through the first plurality ofopenings; reacting the hydrogen-and-oxygen-containing compound with theplasma effluent in the mixing region to form reaction products; flowingthe reaction products through a second plurality of openings in apartition to a substrate processing region; etching the substrate withthe reaction products in the substrate processing region.
 2. The methodof claim 1, wherein: the substrate processing region and the mixingregion are entirely plasma-free.
 3. The method of claim 1, wherein thehydrogen-and-oxygen-containing compound comprises water vapor or analcohol.
 4. The method of claim 1, wherein: the substrate comprises afirst exposed portion comprising silicon oxide and a second exposedportion, the second exposed portion comprises polysilicon, and the firstexposed portion etches at an etch rate over 500 times faster than thesecond exposed portion etches.
 5. The method of claim 1, wherein: thesubstrate comprises a first exposed portion comprising silicon oxide anda second exposed portion, the second exposed portion comprises siliconnitride, and the first exposed portion etches at an etch rate over 200times faster than the second exposed portion etches.
 6. The method ofclaim 1, wherein the reaction products comprise HF₂ ⁻.
 7. The method ofclaim 1, wherein: each opening of a portion of the second plurality ofopenings is not concentrically aligned with an opening of the firstplurality of openings nearest to the respective opening.
 8. The methodof claim 1, wherein: each opening of a portion of the second pluralityof openings is concentrically aligned with an opening of the firstplurality of openings nearest to the respective opening.
 9. The methodof claim 1, wherein the hydrogen-and-oxygen-containing compound is notexcited by a plasma formed by a power applied to the showerhead relativeto the partition.
 10. The method of claim 1, wherein striking the plasmadischarge comprises applying the power from the power supply to aportion of a processing system relative to the showerhead.
 11. Themethod of claim 1, wherein the hydrogen-and-oxygen-containing compoundis not excited by a capacitively coupled plasma or an inductivelycoupled plasma.
 12. The method of claim 1, wherein thehydrogen-and-oxygen-containing compound comprises an alcohol.
 13. Amethod of etching a substrate, the method comprising: striking a firstplasma discharge in a first plasma region with a first power from afirst power supply; striking a second plasma discharge in a secondplasma region with a second power from a second power supply; flowing afluorine-containing precursor into the first plasma region to form aplasma effluent; flowing the plasma effluent into the second plasmaregion; flowing a hydrogen-and-oxygen-containing compound to the secondplasma region; reacting the hydrogen-and-oxygen-containing compound andthe plasma effluent in the second plasma region to form reactionproducts, wherein the hydrogen-and-oxygen-containing compound is notexcited by the first plasma discharge prior to entering the secondplasma region; flowing the reaction products through a plurality ofopenings in a partition to a substrate processing region; etching thesubstrate with the reaction products in the substrate processing region,wherein the plasma effluent and the hydrogen-and-oxygen-containingcompound do not flow through the same opening before entering the secondplasma region.
 14. The method of claim 13, wherein the plasma effluentdoes not flow through a plurality of openings in an electricallygrounded showerhead before the plasma effluent enters the second plasmaregion.
 15. The method of claim 13, wherein the first plasma dischargeis a capacitively coupled plasma or an inductively coupled plasma. 16.The method of claim 13, wherein striking the second plasma dischargecomprises applying the second power from the second power supply to aportion of a processing system relative to the partition.